A brake system for a tractor-trailer vehicle includes a service brake system and a park brake system. The service and park brake systems are used to brake both a tractor and a trailer towed by the tractor. The service brake system includes service brakes that are used to slow or stop the vehicle during normal vehicle operation. The park brake system includes park brakes that are moved between a released position and an applied position where wheel rotation is prevented during a parking phase. The park brake system includes a park brake control valve that receives input from an actuator located within a tractor cab of the vehicle. A vehicle operator controls the park brake control valve and actuator to apply and release park brakes in both the tractor and the trailer.
A trailer hand control valve is also located with the tractor cab and is actuated by the vehicle operator to brake the trailer. The trailer hand control valve is fluidly connected to a tractor protection valve. The tractor protection valve is also fluidly connected to a primary air supply and a secondary, back-up, air supply. Thus, three air connections are required to be routed through the tractor to the trailer. The tractor protection valve is connected to the trailer with glad hands connectors. Air for applying the trailer brakes is communicated from either the primary air supply, secondary air supply, or trailer hand control valve to the tractor protection valve.
Check valves are incorporated into the tractor protection valve to control and direct airflow for applying trailer service brakes. Check valves are also incorporated into the park brake control valve to control and direct air flow to the park brakes on both the tractor and the trailer.
One disadvantage with this traditional configuration concerns the incorporation of the check valves into the park brake control valve and the tractor protection valve. The park brake control valve is located within the tractor cab close to the actuator, which is typically located on a vehicle dash. Further, the park brake control valve is fluidly connected to the primary air supply and the secondary air supply. This requires at least two different air connections to the check valve. These air connections must be plumbed through the tractor, which is difficult due to packaging space constraints. Similarly, incorporating check valves into the tractor protection valve is also difficult due to packaging constraints.
Another disadvantage is that three separate air connections are required to be routed through the tractor to the trailer to provide the appropriate air signals to the tractor protection valve. It is difficult to route and plumb three separate air connections to the tractor protection valve due to limited space constraints. Further, using multiple air connections to the tractor protection valve increases cost and assembly time.
Thus, there is a need for a service and park brake valve assembly that can transmit an air signal from a primary air supply, secondary air supply, or trailer hand control valve to a tractor protection valve without requiring multiple air connections. The service and park brake valve assembly should also eliminate the need for check valves in the tractor protection valve and park brake control valve, in addition to overcoming the other deficiencies in the prior art discussed above.